Quite interesting! One thing to take into account is that perhaps not all of the ancient witnesses are independent. It is quite possible for one of them to write of Sirius as fiery red because he has read this description in some earlier author, without having actually looked (or maybe having looked, but not trusting his own observation).

Is there any chance that some sort of color-blindness on the part of one or two of the writers would explain the event? Or that perhaps some of the less astronomically astute might have confused it with another star?

According to wikipedia

not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius described it as "sea-blue", as did the 4th century Avienus. It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue

I am going to bring up a discussion from the late Issac Asimov. He said that Sirius was most important when it was rising before the Sun in the morning sky. This helical rising marked the flooding of the Nile and other important religious times in the ancient Middle East.

So, we all know that a rising star is shining through a lot of dust in the air. He believed it was reddened by that dust pollution and that when it was in its most important position in the sky to the ancients it was indeed ruddy.

One point which might be made would be concerning the behavior of the star visually. When the very brightest stars are seen either when the seeing is unstable or they are closer to the horizon, they seem to be scintillating violently with radical variations in brightness and sometimes in color. This may give them the appearance of being "fiery" rather than just red in color. Sirius is particularly prone to this effect, especially during the Heliacal rising which was so important to some ancient cultures. Also, not all ancient sources describe Sirius as reddish. The 1st century writer Marcus Manilius (1 A.D) described it as "sea-blue", and so did the 4th century writer Avienus. In addition, the ancient Chinese used Sirius as a sort of "standard" for the color white, with some records in the 2nd century B.C. to the 7th century A.D. also reporting its color as white.

Another factor to consider is that *if* a red giant star was put in place of the current Sirius B white dwarf, Sirius would be much brighter than it appears today (probably in the -4 to -8 magnitude range depending on the mass of the giant), making daylight sightings more common. There should also be at least some evidence (gas or faint nebulosity) of the considerable mass loss around the star from the time before it contracted into its current white dwarf status (especially after so short a time between when it was reported as red to when Sirius was said to be bluish-white). It is an interesting idea of having Sirius-B as a red giant in ancient times, but there is also the possibility that we are misinterpreting what the ancients really meant when they described Sirius as "fiery". Clear skies to you.

Great info!! Very interesting. btw, at this link if you read the last para there is an working astophysics theory that can explain this phenomenon. Very cool when the historical record points out some things we never imaged could have happened. Keeps us on our toes

Robert Burnham Jr. in his celebrated Celestial Handbook also speculates on the ancient ruddines of Sirius. He noted a couple of other instances where things modern folks don't think of as being "reddish" were described with epithets that implied reddish hue.

For example, in the Iliad there are many references to "wine-dark sea". Wine in ancient times was normally red. Of course, there are other explanations. In ancient times there was no clear glass. Wine was drunk from opaque goblets. Pour a nice cabernet into a stoneware mug, and I can unserdstand how the inky liquid might mimick the darkend surface of a stormy Aegean.

I wonder if there's a possible explanation around air quality. Sirius is brilliant, and still relatively low in elevation in Greece and Mesopotamia. Could some combination of wood fire smoke and perhaps increased levels of volcanic activity in the Mediterranean be responsible for Sirius' fiery appearance?

On especially turbulent nights, when Sirius is near the horizon, I find that refraction causes it to briefly flash many colors other than blue-white. Perhaps some of the ancients meant "fiery" as in animated and flickering rather than "fire-colored"?

At any rate, this is one of my favorite CN articles of all time. A thousand thanks for posting it!

I am going to bring up a discussion from the late Issac Asimov. He said that Sirius was most important when it was rising before the Sun in the morning sky. This helical rising marked the flooding of the Nile and other important religious times in the ancient Middle East.

So, we all know that a rising star is shining through a lot of dust in the air. He believed it was reddened by that dust pollution and that when it was in its most important position in the sky to the ancients it was indeed ruddy.

This is a good point to raise because of how important heliacal risings and settings of celestial objects were in most ancient cultures. One of the replies is that no ancient author calls Canopus white even though that important star never got very far above the horizon and therefore would have been even more vulnerable to atmospheric effects than Sirius.

A couple of responses have brought up the statement of Marcus Manilius regarding Canis Major. A careful reading of the original Latin reveals that it is not Sirius that Manilius says is blue, but the "face" of the Dog. Sirius was regarded as marking the mouth of Canis Major. Manilius calls Delphinus "dark blue"--a statement certainly not applicable to any of its stars, which are too faint to reveal color to the unaided eye. Manilius seems to have used the idea of constellation color in a peculiar way--perhaps related to astrology, which was, after all, the main topic of his book.

A striking feature of the ancient testimony to the redness of Sirius are the variety of authorities who report it. Both Ptolemy and Geminos were clearly men intimately familiar with the night sky and not likely to make an error on such an important point. Germanicus was a field general in the Roman Army who would have seen the star under a variety of conditions. Columella was a practising agriculturalist. It is inconceivable that such a group of highly intelligent men whose knowledge of the heavens came from such a variety of experiences would have simply repeated the same mistake.

Thanks for the great article. The ensuing thread has been pretty great too. The actual color of Sirius during ancient times is surely one of the more interesting mysteries in the history of astronomy. It is too bad we can't go back in time to see for ourselves whether the Dog used to be red...

I am going to bring up a discussion from the late Issac Asimov. He said that Sirius was most important when it was rising before the Sun in the morning sky. This helical rising marked the flooding of the Nile and other important religious times in the ancient Middle East.

So, we all know that a rising star is shining through a lot of dust in the air. He believed it was reddened by that dust pollution and that when it was in its most important position in the sky to the ancients it was indeed ruddy.

This is a good point to raise because of how important heliacal risings and settings of celestial objects were in most ancient cultures. One of the replies is that no ancient author calls Canopus white even though that important star never got very far above the horizon and therefore would have been even more vulnerable to atmospheric effects than Sirius.

A couple of responses have brought up the statement of Marcus Manilius regarding Canis Major. A careful reading of the original Latin reveals that it is not Sirius that Manilius says is blue, but the "face" of the Dog. Sirius was regarded as marking the mouth of Canis Major. Manilius calls Delphinus "dark blue"--a statement certainly not applicable to any of its stars, which are too faint to reveal color to the unaided eye. Manilius seems to have used the idea of constellation color in a peculiar way--perhaps related to astrology, which was, after all, the main topic of his book.

A striking feature of the ancient testimony to the redness of Sirius are the variety of authorities who report it. Both Ptolemy and Geminos were clearly men intimately familiar with the night sky and not likely to make an error on such an important point. Germanicus was a field general in the Roman Army who would have seen the star under a variety of conditions. Columella was a practising agriculturalist. It is inconceivable that such a group of highly intelligent men whose knowledge of the heavens came from such a variety of experiences would have simply repeated the same mistake.

Interesting, but there is really no possibility that Sirius was actually red. I think it's much more likely the authors are referring to the colorful scintillations we've all seen when Sirius is in clear air on a cold night, or close to the horizon. Sometimes Vega does this as well - so it would be interesting to see what the old authors said about that star. And for comparison, Rigel, Antares, Arcturus, and Capella.

A red giant at 8.6 light years would be a spectacular sight, much less a nova at that distance - so I don't think there is any hope of explaining a ruddy Sirius as being due to Sirius-B in an earlier life. Antares and Betelgeuse are resp. ~600 and ~500 light years distant. So 100-fold change in distance for them would increase their brightness 10,000 times or 10 magnitudes, to near that of the full Moon!

If there was a color shift, you would think that someone would have noticed and remarked on it. Even if they didn't witness the actual "event", the change in color of such a significant star would certainly have been something worth noting - even as a portent of some sort.

Is it possible that Sirius B made the transition from red giant to white dwarf over the span of a couple of thousands of Earth year?

Were the Sirius system composed differently a few thousand years ago, consisting of a brilliant blue-white star and a contracting red giant, the apparent color of the combined light of the system that *could* have been actually red.

Of course, the theory of stellar evolution for red giants into white dwarfs predicts a billion+ year transition (often with a planetary nebular phase during the early part of transition).

Another somewhat far fetched possibility is a change in human ocular physiology in the intervening millennia. What if the human eye perceived certain colors differently? Alternately, what if ancient populations had a much higher incidence of male color blindness than do modern populations? I note that the sources quoted are all males, likely due to the patriarchical social structures of those cultures being sampled.

Are there any surviving female accounts of the color of Sirius? I wonder if any of Sappho's lost works mentioned Sirius?

If there was a color shift, you would think that someone would have noticed and remarked on it. Even if they didn't witness the actual "event", the change in color of such a significant star would certainly have been something worth noting - even as a portent of some sort.

This is a good point. The problem was that as early as the 3rd century AD Europe was beginning to slip into the Dark Ages. In effect astrology had completely displaced astronomy by the 4th century and very few people were really looking at the stars any more, just repeating what earlier astrological writers like Manilius--and Ptolemy himself in his "Tetrabiblos," which is work on astrology--had said. By then social, political, and economic conditions were terrible, and virtually nobody had the will or leisure to do real astronomy anyway.

During the depths of the Dark Ages 'star-gazing' was associated with astrology, which was under interdiction by the Church. Any real astronomy that was done in the centuries around 1000 AD was being done by Near Eastern astronomers writing in Arabic; but their contributions to Classical Ptolemaic astronomy was negligible. The most "scientific" of these medieval Arabian astronomers seem to have been Al-Sufi of the 10th century and Al-Buruni of the 11th century. The stars Al-Sufi (903-986) mentions as red are Aldebaran, Arcturus, Antares, Betelgeuse, Pollux, and, strange to say, Alphard and Algol. He says nothing specifically about the color of Sirius, but does relate an Arabian myth in which Sirius and Canopus appear as sisters, implying a similar color. Al-Sufi thus gives strong, but not conclusive, evidence that Sirius had changed in color by the 10th century.

While there are Chinese accounts from the 7th Century describing Sirius as "white" there are also at least one 6th Century European account describing Sirius as reddish. Gregory of Tours in a writing directed at monks nicknamed Sirius as "Rubela" meaning reddish.

Your point that Sirius and Canopus were regarded as "sisters" in 10th Century Arabic astronomical writings is very interesting. To me Canopus is white. Perhaps a little yellowish tinged, but certainly not red. I could call Sirius white as well, perhaps with a little tinge of blue.

If the Gregory of Tours lead is correct (6th Century), that would suggest that the color change might have occurred between the 6th and 7th Centuries (i.e., Chinese observers in the 7th Century call Sirius white; a European writer in the 6th Century calls it "Rubela").

Are there any post-6th-Century accounts of a red Sirius? How about pre-6th-Century accounts of a "white" Sirius? Are any of these accounts scientifically credible? For example, can we be sure that the authors weren't simply repeating color attributions from earlier writings rather than basing their color attributions on first-hand observations?

Through all this, we assume that the star the ancients were talking about is the *same* star, and not another bright star in the same vicinity.

If there was a brighter star in the vicinity (thus referred to as the brightest star in that area of the sky), and it dimmed substantially in the last 2000 years, could we not mistaken their references to the red star as Sirius simply because that's the brightest star *we* see in that region of the sky? How can we be so certain that there wasn't another brighter star?

Just like the constellations have altered in brightness (and configuration a bit) in recent times (which is why we see different asterism than the people who named the constelations on most nights), we might also have evidence here that there was another *brighter* star in the vicinity of Sirius. So far, I haven't seen any evidence either way as to whether the star we call Sirius is indeed the same star that the ancients referred to.

Could it be possible that there was a cloud of perhaps carbon surrounding the system that slowly dissipated? Or could there have been a line of sight background star that was in its red giant phase at the time?

The history of astronomy is remarkable because it ties us the knowledge of the men of old. For what is ancient to mankind is just a cosmic twinkle. We share the essentially same sky. A red Sirius is a facinating puzzle.

If it's red appearance applies the heliacal rising, then why are not other white stars such Rigel also described?

It's possiblity of being misidentified is doubtful since the entire Egyptian calendar was based on Sirius = Sothis. The expectation of the annual Nile flooding was based on the morning rising of Sothis. Babylonians named and described it as the arrow of a bow and arrow constellation. It was identity was common knowledge and was an object of worship of many civilizations.

I really enjoyed reading this fine article, and the discussion it has generated.

Because several of the bright stars are noticeably red, a certain "importance" tot the color red would be a given.Since Sirius is so bright, the description of Sirius as "red" could be as much a cultural identification as a spectral one. After all, many kings through the middle ages are described as tall and stately when their coffins indicate they were barely 5 feet tall--short even in the middle ages.So it would be wise to take such ancient writings with a grain of salt. They may not have been describing an empirical observation. Remember the scholarly debate about the number of teeth in the horse's mouth? Empiricism was not a phenomenon of the Roman Era or even what followed.Ascribing literalist interpretations to ancient writings is fraught with danger.

One of the most important aspects of the question of an ancient red Sirius is the intellectual sophistication of the ancient authorities who report Sirius as red. These were neither credulous nor gullible men. The genius of Ptolemy is beyond dispute, and it is clear that he was not a merely a "desk astronomer" but an active observer (working from Alexandria, Egypt, the intellectual capital of the eastern Mediterranean at that time).

Cicero, Germanicus, and Seneca, all of whom report Sirius to be red, were deeply involved in the snake-pit of Roman politics of the 1st centuries BC and AD. Cicero, one of the geniuses of Latin literature and deeply read in all aspects of Greek philosophy, held the consulship--the highest post in the Roman Republic--in 63 BC, and later used his influence to attempt a reconcilation between Pompey and Julius Caesar. Modern American law claims decent from Roman Republican law, one of the chief interpreters of which was Cicero.

Germanicus was a member of the Julio-Claudian family, from which derived the Roman Emperors from Augustus to the notorius Nero. He was nephew of Tiberius and such a capable field general that there were those who said Germanius, not Tiberius, should be Emperor. During the reign of Augustus a Roman force had been ambushed in the forests of Germany and lost three legionary standards--a great disgrace. Germanicus had the difficult and unenviable task of crossing the Rhine and avenging this defeat. He died at a young age (rumors had it that he was poisoned on orders of Tiberius) but his son Caligula followed Tiberius as Emperor.

Finally Seneca was a Stoic philosopher who also wrote for the Roman theater. He was the tutor of the future Emperor Nero, who, when he first assumed the purple, began well. But Nero was too weak to resist the hedonistic possibilities of his position. He knew the Stoics, several of whom were also prominent senators, disapproved of him on both political and moral grounds. This put Seneca in a very delicate position, and he retired from public life to devote himself to his studies and writing. He did not want to end up like Germanicus, so he took such precautions as eating fruit only from his own garden. Eventually, however, Nero "suggested" that it was time for Seneca to commit suicide.

I go into some detail on these men's lives to make the point that they were hard minded and sophisticated--well-travelled, widely-read, and experienced in life-and-death matters in a complicated political setting. Not the kind of men easily duped or quick to take anybody's word for anything. None of them 'bought into' the Paganism of their time: Cicero was a self-avowed agnostic with Stoic leanings; and Seneca, as a Stoic, was a Deist. And they took great pride in their writing and intellectual accomplishments. In those days such things were taken much more seriously than they are in present Western culture, and Cicero, Germanicus, Julius Caesar, and Seneca did not write carelessly, or just to fill in idle time, but knew that their historical value would be judged as much by their intellectual as their political accomplishments.

Yes, this is all very nice, but the question is; are we interpreting what they wrote properly and accurately? Do we really know exactly what they meant? There appears to be some question here as to whether they really meant that Sirius was red all the time no matter where it was in the sky or just behaved in a "fiery" manner due to scintillation. From an astrophysical point of view, there is no evidence that Sirius-B was a red giant in historic times. There is also some contradictory evidence from other writers or observers that Sirius was reported as white rather than red:

Again I would point out the simple calculation of the apparent brightness of say Betelgeuse or Antares at the distance of Sirius, roughly 100 times closer than either. The laws of light propagation show that the surface brightness does not change with distance - now something that is 100 times closer will have 100^2 or 10,000 times the area as something of the same physical size at the original distance - assuming that each part of the star shines with the same brightness (more or less, discounting fall-off at the limb) then moving a star 100 times closer means making it 10,000 times brighter - now 5 magnitudes is a factor of 100, so we're talking about a magnitude difference of 10 - Betelgeuse at the distance of Sirius would be magnitude -10 roughly, more than 100 times brighter than Venus - it would cast shadows at night and be visible in daylight without any effort. So there is not really any possibility that Sirius-B or any other nearby star was a red giant in historical time.

Again I would point out the simple calculation of the apparent brightness of say Betelgeuse or Antares at the distance of Sirius, roughly 100 times closer than either. The laws of light propagation show that the surface brightness does not change with distance - now something that is 100 times closer will have 100^2 or 10,000 times the area as something of the same physical size at the original distance - assuming that each part of the star shines with the same brightness (more or less, discounting fall-off at the limb) then moving a star 100 times closer means making it 10,000 times brighter - now 5 magnitudes is a factor of 100, so we're talking about a magnitude difference of 10 - Betelgeuse at the distance of Sirius would be magnitude -10 roughly, more than 100 times brighter than Venus - it would cast shadows at night and be visible in daylight without any effort. So there is not really any possibility that Sirius-B or any other nearby star was a red giant in historical time.

-drl

The current mass of the Sirius-B white dwarf is on the order of one solar mass. This points to an original mass of around five solar masses for the star prior to its white dwarf stage, so any red giant phase star would not have had nearly the intrinsic brightness of red giants like Betelgeuse (at least 18 solar masses) or Antares (15 to 18 solar masses). The absolute magnitude of a five solar mass red giant would probably be in the -3 to -4 range depending on exactly where the star was in its red giant stage. At the distance of Sirius, that would make the giant a visual magnitude of between roughly -7.6 and -8.6 even without including the contribution of Sirius A itself. It would shine far brighter than Venus does and might be roughly comparable to the brightness of a first-quarter moon. Clear skies to you.

Taking a look at (my complete though very ancient) Lidell and Scott, "hypokirros" (assuming this is the word you transliterate as hypocirros) has only "somewhat yellow" as the definition and a scant 2 references, neither to Ptolemy. "Kirros" (of which the word in question is a compount) is defined as "tawny, orange-tawny, between purros and xsanthos". There is definitely a yellow component implied, in my opinion. Perhaps there are newer and better definitions available?

Rutilus, according to the OLD (Oxford Latin Dictionary) is often taken to mean glowing red, but also can be taken as "golden" or "orange" and definitely has associations with fire and the rising sun, but also to the hair color of ancient Germans (yellow or reddish blond, pehaps?), the color of metallic gold, etc. It may be in the secondary sense that rutilus is considered a proper translation, i.e., warm and brilliant.

As far as I'm concerned, the fact that Cicero and the others translated a word probably meaning "somewhat yellow" with a word maybe meaning "red" or "golden" or even "tawny" probably means nothing, except that they understood more about the ancient conceptions of color than we do. Try reading Isidore's classification on the different colors of horses, for a nice demonstration on just how seriously the ancients took these things at times.

Unfortunately, all of the Roman authors you cite are in fact little more than translators (or perhaps re-organizers) when it comes to scholarly works on natural science, though their importance to history is great, as you say. Which is to say that they probably translated to the best of their considerable abilities, but most likely never bothered to verify the material. In this case, the "redness" of rutilus (the translation) is far more convincing than the original term, but far from unambiguous.

Anyway, I don't agree that Sirius must necessarily have been percieved by the Greek and Latin sources cited as "red", but I did enjoy your article immensely and want to stress that this is just my understanding and an attempt to further the conversation.